Akylthio substituted polynuclear phenols

ABSTRACT

Alkylthio substituted polynuclear phenolic age resisters and age resistant polymers containing said age resisters.

United States Patent 1 Spacht Apr. 17, 1973 AKYLTHIO SUBSTITUTED [56] References Cited P L UCLEAR PHE HS 0 YN NO UNITED STATES PATENTS [75] Inventor: Ronald B. Spacht, Hudson, Ohio 1 3,423,389 12/1969 Wheelus ..260/609 F X [73] Assignee: The Goodyear Tire 8: Rubber Com- 3,320,163 5/1967 Abbott et al.... ..260/608 X pany Akron Morway 6t F 3,035,908 5/1962 Gottshall et a]. ....260/609 F X [22] Fll d: m- 1970 2,346,826 4 1944 Cook et a1. ..260/608 Appl. No.: 71,230

Related US. Application Data Division of Ser. No. 664,601, Aug. 30, 1967, Pat. No. 3,565,857.

Primary Examiner--Lewis Gotts Assistant Examiner-D. R. Phillips Attorney-F. W. Brunner and Vernon G. Parker Alkylthio substituted polynuclear phenolic age resisters and age resistant polymers containing said age resistors.

4 Claims, N0 Drawings AKYLTHIO SUBSTITUTED POLYNUCLEAR PHENOLS This is a division of application Ser. No. 664,601, filed Aug. 30, 1967 and which issued on Feb. 23, 197], as U.S. Pat. No. 3,565,857.

This invention relates to age resistors for oxidizable organic materials, their preparation and use in the stabilization of polymers which normally tend to deteriorate when exposed to normal atmospheric conditions and in particular when exposed to sunlight and/or elevated temperatures in the presence of air or oxygen.

Polymers have proven to be some of the most difficult organic materials to successfully stabilize against the deleterious effects of oxygen and ozone, particularly rubbery polymers, both natural and synthetic. Both vulcanized and unvulcanized polymers are susceptible to the deleterious effects that are found in normal atmospheric conditions, and although many materials have keen suggested and used as polymer staradicals containing from one to 12 carbon atoms, cycloalkyl radicals containing from five to nine carbon atoms and aralkyl radicals containing from seven to nine carbon atoms, and R and R are bivalent radicals selected from the group consisting of bivalent organic radicals and bivalent inorganic radicals and wherein n is a positive integer from to 3.

Preferably R, R and R are alkyl radicals containing from one to l2 carbon atoms.

When n equals 2 or 3 the antioxidant molecule will contain two or three R" radicals as well as two or three R radicals. In such cases the R radicals need not necessarily be identical, nor must the R radicals neces-' sarily be identical. Examples of specific compounds that conform to the above recited structural formula are represented below by a listing of specific radicals, any combination of which in the structural formula (1) above represents a specific compound within the scope of thepresentinvention,

R and R R, R and R R and R n H CH;; -CH: 0 CH: C2H5- S l C2H5- H7 -SS- 2 CzH7- CtHr- ("U 3 otr-m fill:

(HIIr- Usllu Y c orraomcngon Cslirv- CaHr7-- -(']'I:('ll -'('ll'Cllg nlIi1- (liaHs- -C H2 0 I Gll:-

CnHuwherein, R, R and R are hydrocarbon radicals containing from one to carbon atoms, R and R are selected from the group consisting of hydrogen, alkyl- III 1 The alkyl groupings may be primary, secondary or tertiary.

Preferred compounds of the present invention are those which conform to the above structural formula (I) wherein R and R are tertiary alkyl radicals containing from four to 12 carbon atoms.

Specific examples of these preferred compounds are represented below by a listing of specific radicals any combination of which in structural formula (I) above represents a specific compound within the scope of the present invention.

. tertiary butyl CH; --CH, 0 tertiary amyl C H,, --S- l tertiary hexyl C H,- SS- 2 tertiary heptyl C,H CH3 3 tcritary octyl C,,H CH3 tertiary nonyl C H,, -CH,CH,-CH,CH\

Even more preferred compounds are those wherein R and R are tertiary alkyl radicals containing from four to 12 carbon atoms and are located ortho to the phenolic hydroxyl group and wherein R and R are bivalent radicals selected from the group consisting of (A) -S-, (B) S S-; and (C) an organic radical tertiary dodecyl containing from one to 14 carbon atoms.

The most preferred compounds are those which conform to above structural formula (I) wherein R, R and R are selected from the group consisting of methyl,

- ethyl, propyl and isopropyl radicals, R and R are tertiary alkyl radicals containing from four to eight carbon atoms and located ortho to the phenolic hydroxyl groups and R and R are selected from the group conmid (I sisting of S, CH,,

til

and n is a positive integer from 0 to l.

Specific examples of the most preferred compounds are as follows:

2,2'-methylene bis( 4-methylthio phenol) 2,2-methylene bis(4-methylthio-6-tertiarybutyl phenol) 2,2-butylidene bis(4-ethylthio phenol) 2,2'-butylidene bis(4-ethylthio-6-tertiarybutyl phenol) 2,2'-thio bis(4-methylthio phenol) 2,2'-thio bis( 4-methylthio--tertiarybutyl phenol) 2,2-dicyclopentadienyl bis(4-methylthio phenol) 2,2-dicyclopentadienyl bis(4-methylthio-6-tertiarybutyl phenol) 6,6'-methylene bis(3-methylthio phenol) 4,4-methylene bis( 3-methylthio phenol) 2,2-methylene bis(3-methylthio phenol) 4,4-methylene bis(3-methylthio--tertiarybutyl P en 2,2'-methylene phenol) Particularly preferred are 4,4-methylen'e bis(3# methylthio-o-tertiarybutyl phenol) and 2,2'-methylene bis( 4-methylthio--tertiarybutyl phenol).

The compounds of this invention may be prepared by a one step or a two step method. The one step method comprises reacting a mixture comprising (A) at least one phenolic reactant and (B) at least one condensation reactant. The phenolic reactant conforms to the following structural formula:

bis (3-methylthio-6-tertiarybutyl wherein R is a hydrocarbon radical containing from one to 20 carbon atoms and R is selected from the group consisting of hydrogen, alkyl radicals containing from one to 12 carbon atoms, cycloalkyl radicals containing from five to nine carbon atoms and aralkyl radicals containing from seven to nine carbon atoms. Preferably R is an alkyl radical containing from one to 12 carbon atoms.

Examples of specific compounds that conform to the above recited structural formula are shown below. 3-methylthio phenol 4-methylthio phenol 2-methylthio phenol 4-ethylthio phenol 3-propylthio phenol 4-octylthio phenol 2-tertiarybutyl-4-methylthio phenol 3-pr0pylthio-6-tertiaryoctyl phenol 3-methylthio-5-methyl phenol 2-ethyl-4-ethylthio phenol Preferred phenolic reactants for the one step method are those according to structural formula (II) wherein R is selected from the group consisting of methyl, ethyl,

propyl and isopropyl radicals and wherein R is a tertiary alkyl radical containing from four to eight carbon atoms and located ortho to the phenolic hydroxyl p- 7 Examples of these preferred phenolic reactants are as follows:

2-tertiarybutyl-4-methylthio phenol 3-methylthio-6-tertiaryamyl phenol 3-propylthio-6-tertiaryoctyl phenol 2-tertiaryheptyl-4-ethylthio phenol The most preferred phenolic reactant in the one step method is 2-tertiarybutyl-4-methylthio phenol.

The condensation reactant is a material selected from the group consisting of aldehydes; ketones; sulfur monochloride; sulfur dichloride; dihalo alkenes containing from four to carbon atoms; di(halomethyl) diphenyl oxides; a,a'-dihalo xylenes and dicyclopentadienes.

Examples of aldehydes which may be used in the practice of the present invention are as follows:

formaldehyde acetaldehyde propionaldehyde butyraldehyde isobutyraldehyde paraldehyde paraformaldehyde valeraldehyde Examples of ketones which may be used as condensation reactants are as follows:

acetone methyl ethyl ketone methyl isobutyl ketone methyl isoamyl ketone diethyl ketone methyl propyl ketone Examples of dihalo alkenes which may be used are:

1,4-dichlorobutene-2 2-methyl-1,4-dichlorobutene-2 2,3-dimethyl-l ,4-dichlorobutene-2 1,4-dichlorohexene-2 Examples of di(halomethyl) diphenyl oxides are:

4,4-di(chloromethyl)-diphenyl oxide 4 ,2'-di(chloromethyl)-diphenyl oxide 2,4di(chloromethyl)-diphenyl oxide Examples of dicyclopentadienes are:

methyl cyclopentadiene dimer cyclopentadiene dimer Some of the compounds of the present invention can be prepared by a two step method. The two step method comprises reacting in the first step a mixture comprising (A) at least one phenolic reactant and (B) at least one condensation reactant and subsequently in the second step reacting the product of the first step with at least one compound selected from the group consisting of olefins containing from two to 12 carbon atoms, cycloolefins containing from five to nine carbon atoms and arylalkenes containing from seven to nine carbon atoms. v

An active halogen compound in some instances can also be used in the second step of the two step method. For example, a compound such as benzyl chloride can be reacted with the product of the first step, normally in the presence of FriedeLCrafts type catalysts'to provide an aralkyl substituent.

in the two step method the phenolic reactant conforms to the following structural formula:

s-R 1m wherein R is a hydrocarbon radical containing from one to 20 carbon atoms. Preferably R is an alkyl radical containing from one to 12 carbon atoms.

Specific examples of materials conforming to the above recited structural formula are as follows:

Z-methylthio phenol S-methylthio phenol 4-rnethylthio phenol 3-ethylthio phenol 4-isopropylthio phenol Z-n-butylthio phenol 3-isoamylthio phenol 4-hexylthio phenol 3-octylthio phenol 4-dodecylthio phenol Preferred phenolic reactants for the two step method are those conforming to structural formula (III) wherein R is selected from the group consisting of methyl, ethyl, propyl and isopropyl radicals.

Examples of these preferred phenolic reactants are as follows:

2-methylthio phenol 3-methylthio phenol 4-methylthio phenol S-ethylthio phenol 4-isopropylthio phenol 4-propylthio phenol 2--ethylthio phenol 4-ethylthio phenol The most preferred phenolic reactants in the two step method are 3-methylthio phenol and 4-methylthio phenol.

The condensation reactant in the two step method is of the same type used in the one step method.

Representative examples of the olefin type materials that can be used in the second step of the two step method are:

l-propene l-butene l-pentene Z-pentene 2-methyll -propene Z-methyll -butene 2-methyl-2-butene Z-methyll -pentene 2-methyi-2-pentene 3-methyl-2-pentene Z-rnethyll -hexene Z-methyhZ-hexene 3-methyl-2-hexene 3-methyl-3-hexene 2,4,4-trimethyll -pentene cz-methylstyrene vinyl toluene cyclohexene styrene methyl cyclohexene methyl cyclopentene The most preferred olefins are tertiary olefins possessing four to 12 carbon atoms such as some of those listed above.

The one step method and the first step of the two step method are carried out in essentially the same manner. The reactions for the one step method and the first step of the two step method will vary with the condensation agent. With aldehydes and ketones an acidic catalyst is preferred and the condensation can be carried out by gentle heating. For best results a low boiling solvent capable of azeotropically removing the water as formed is desirable although not necessary. With the active dihalogen compounds such as 1,4 dichloro-butene-2; 4,4'-di(chloromethyl) diphenyl oxide and 01,01- dichloro xylenes heat may be necessary along with small amounts of a Friedel-Crafts catalyst. This will depend upon the activity of the dihalo compound. Satisfactory reactions with diolefins as dicyclopentadiene are obtained with B1 Alkylation, particularly tertiary alkylation, in positions ortho to the hydroxyl groups provides a superior product. Tertiary alkyl groups having four to 12 carbon atoms, and therefore tertiary olefins containing from four to 12 carbon atoms, are preferred. Such alkylated products may be prepared by the one stage-or two stage methods. In the one stage method as alkylated, alkylthio phenol is reacted with the condensation reactant. In the two stage method an alkylthio phenol is reacted with the condensation reactant. The resulting product is isolated, dissolved in a suitable solvent, and alkylated with an olefin using a Friedel-Crafts type catalyst, such as toluene sulfonic acid, anhydrous aluminum chloride, anhydrous ferric chloride and sulfuric acid.

Temperatures used for the second step of the two step method are from 20 to 150 C. In general, reactions involving halides will be at higher temperatures than those involving alkylation with olefins. Preferred temperatures for reactions involving elimination of hydrogen halide are from 100 to 150 C. Preferred temperatures for alkylation reactions are from 60 to 100 C.

The charge ratios of the reactants is normally from 1.5 mols of phenolic compound/mol of condensation agent to 5 mols of the phenolic compound/one mol of condensation agent. In the one step method it is preferred to use a solvent and slightly more than one mol of the condensation agent with every two mols of the phenol when the phenol possesses another substituent in addition to the alkylthio substituent. In the two step method and in the one step method where the phenolic reactant does not contain another substituent in addition to the alkylthio grouping it is preferred to use no solvent in the reaction between the phenolic reactant and the condensation reactant. In addition, a preferred ratio of the phenolic reactant to the condensation reactant is 5 mols of the former to one mol of the latter. Among the suitable inert solvents which may be used in the condensation and alkylation reactions are benzene, toluene, xylene, hexane, cyclohexane, carbon tetrachloride and chloroform.

In the two step method the amount of olefin used should be about one to about two mols of olefin per mol of the product of the first step.

Being more specific concerning the condensation reactions, where aldehydes or ketones are the condensation reactants it is preferred that the condensation reaction be run in the temperature range of about 25 to 150 C., preferably at the reflux temperature of the solvent used. Acid catalysts can be used in such condensation reactions.

Where the condensation agent is sulfur monochloride or sulfur dichloride the reaction temperature can be approximately 25 to 150 C., preferably between 25 and C. No catalyst is necessary for this condensation reaction.

Where dihalo xylenes are used the reaction temperature can be to 175 C., preferably to C. and the reaction can be catalyzed with a Friedel-Crafts catalyst.

The dihalo alkenes can be reacted at a temperature of 50 to 150 C., preferably at 80 to 120 C., in the presence of a Friedel-Crafts catalyst. I

The di(halomethyl) diphenyl oxides can be reacted with the phenolic reactants in a temperature range of 25 to 175 C., preferably 50 to 100 C. The reaction will take place without the presence of a catalystfI-lowever, it is preferred to use a small amount of Friedel- Crafts catalyst, for example, 0.2 to 5.0 parts for 100 parts of thioalkyl phenol.

The dicyclopentadienes can be reacted from 50 to 150 C., preferably from 75 to 100 C. in the presence of a Friedel-Crafts catalyst. Boron. 'trifluoride is a preferred catalyst.

The following Examples 1 through 9 showing the preparation of compounds conforming to the present invention are intended to be illustrative of the class of compounds disclosed and the method of their preparation but are not to be interpreted as limitations of the invention.

EXAMPLE 1 One hundred and fifty-four grams of 4-(methylthio) m-cresol were dissolved in 200 milliliters of hexane. 2 milliliters of concentrated hydrochloric acid were then added. This mixture was heated to 60 C. and 50 grams of formalin (37.5 percent formaldehyde) was added in I 0.5 hour. The mixture was then heated under reflux using a water trap. All of the. water was removed in 3 hours. Finally the mixture was heated to pot temperature of C. at 3 millimeters of mercury to remove unreacted materials. The yield was 173.0 grams of product.

EXAMPLE 2 Two hundred milliliters of toluene and 8.0 grams of concentrated sulfuric acid were added to the product from Example I. The mixture was heated to 100 C. Isobutylene was then added over a period of 4 hours. The catalyst was then neutralized with aqueous sodium carbonate. The aqueous layer was decanted from the mixture and the remainder of the mixture heated to 150 C. to remove any volatiles.

EXAMPLE 3 EXAMPLE 4 of toluene sulfonic acid added to the mixture. It was heated to 100 C. and isobutylene added over a period of several hours. The mixture was then neutralized with aqueous sodium carbonate and digested. The aqueous layer was then decanted. The mixture was heated to 150 C. at 20 millimeters of mercury toremove the volatiles. The weight of the reaction product was 160 grams.

' EXAMPLE 5 One hundred and fifty grams of 4(methylthio)-metacresol and 200 milliliters of toluene were heated together to 70 C. 134 grams of a commercial -di(chloromethyl) diphenyloxide (CMDPO-25) were added to the mixture over a period of 1.5 hours. Heating was continued for several hours. The mixture was then heated to 150 C. at 20 millimeters of mercury to remove the solvent and any unreacted materials. The weight of the reaction product was 250 grams.

EXAMPLE 6 EXAMPLE? One hundred and forty grams of para-(methylthio) phenol were reacted with 134 grams of di(chloromethyl) diphenyloxide in the manner described in Example 5. The yield was 239.0 grams of product.

EXAMPLE 8 One hundred and thirty-nine grams of product from Example 7 were butylated in the manner described in Example 7. The yield was 158 grams.

The compounds of this invention are useful in protecting polymer in any form, e.g., polymer in latex form, unvulcanized polymer and vulanized polymer. The method of addition of the antioxidant to the polymer is not critical. They may be added by any of the conventional means such as by adding to a polymer latex, milling on an open mill or by internal mixing. They are highly efficient and are capable of being employed in relatively small amounts to effectively stabilize the polymers into which they are incorporated. Normally 0.001 to 5.0 percent of the antioxidant by weight based on the weight of the polymer can be used, although the precise amount of these highly effective stabilizers which is to be employed will depend somewhat on the nature of the polymer and the severity of the deteriorating conditions to which the polymer is to be exposed. ln unsaturated polymers such as those made from conjugated dienes, the amount of antioxidant necessary is greater than that required by a saturated polymer such as polyethylene. lt has been found that an effective antioxidant of the disclosed stabilizers in rubbery polymers will generally range from 0.05 to 5.0 percent by weight based on the weight of the polymer although it is commonly preferred to use from 0.5 to 2.0 percent by weight based on the weight of the polymer.

The polymers that may be conveniently protected by the phenolic compounds in accordance with this invention are vulcanized and unvulcanized oxidizable rubber and those synthetic oxidizable polymers which are normally susceptible to deterioration by sunlight and atmospheric oxygen such as prepared from conjugated dienes as well as the synthetic polymers and copolymers prepared from monoolefins. Representative examples of the synthetic polymers used in the practice of this invention are polychloroprene; homopolymers of a conjugated l,3-diene such as isoprene and butadiene and in particular, polyisoprenes and polybutadienes having essentially all of their segmeric units combined in a cisl ,4 structure; copolymers of a conjugated 1,3 diene such as isoprene'and butadiene with up to 50 percent by weight of the polymer of at least one copolymerizable monomer such asv styrene and acrylonitrile; butyl rubber, which is a polymerization product of a major proportion of a monoolefin and a minor proportion of amultiolefin such as butadiene or is0prene; and polymers and copolymers of monoolefins containing little or no unsaturation, such as polyethylene, polypropylene, ethylene propylene copolymers and terpolymers of ethylene, propylene and a nonconjugated diene.

The practice of this invention is found particularly beneficial when applied to the stabilization of homopolymers of a conjugated 1,3-diene such as isoprene and butadiene and copolymers of said diene with up to 50 percent by weight of at least one copolymerizable monomer acrylonitrile. The practice of this invention is found most beneficial when applied to the stabilization of copolymers of butadiene and styrene.

The stabilizers of this invention can be added to polymers by any of the conventional procedures, that is, directly to the polymer by milling or internal mixing, a latex or solution form of the polymer, etc.

In order to evaluate the effectiveness of the compounds of this invention as stabilizers for polymers representative compounds of this invention were incorporated into an oxidizable polymer.

EXAMPLE 9 The products produced in the previous examples were evaluated in SBR-I006 (a hotemulsion polymerized butadiene/styrene rubber) by oxygen adsorption at C. (Experiments D through K). Also evaluated was an unstabilized SBR 1006 (Experiment A) and two SBR 1006 samples stabilized with two phenolic antioxidants not within the practice of the present invention (Experiments B and C). One part of antioxidant was used in each experiment. The data are summarized below in Table l. The oxygen absorption tests were conducted by dissolving in benzene portions of an SBR polymer (1006) containing 1.00 part per 100 parts of rubbery polymer of various antioxidant such as styrene and compositions of this invention. The cements so formed .to absorb 1.0 percent oxygen was determined and recorded in the following table. This testing procedure is describedin further detail in Industrial and Engineering Chemistry, 43, p. 456 (1951) and Industrial and EngineeringChemistry, 45, p. 392 (1953).

TABLE I Oxygen Absorption Experiment Antioxidant Hours to 1% O, A No antioxidant 4 ,B 4(methylthio) phenol 71 C 4(methylthio)-m-cresol 88 D R.P.* of 4(methylthio) -m-cresol and 199 formaldehyde E Butylated D (Example 3) 181 F R1. of 4(methylthio) phenol and 120 formaldehyde G Butylated F (Example 5) 201 H R.P. of 4(methylthio)-mcresol and 103 CMP-25( Example 6) 103 l Butylated H (Example 7) 140 J R:P. of 4(methylthio phenol and 84 CMDPO-25"(Example 8) K Butylated .1 (Example 9) I51 Reaction product l Di(ehloromethyl) diphenyloxide These results demonstrate the superior activity of the compounds of the present invention (Experiments D tice of the present invention in polypropylene but is not intended to so limit the invention.

EXAMPLE 10 Polypropylene (Pro-Fax 6501) was stabilized with 0.10 part of seven different stabilizers within the scope of .the present invention (Experiments N through T). Another portion of the polypropylene was stabilized with 0.10 part of 2,6-ditertiary-butyl-p-cresol. The yield tensiles and melt indices of these stabilized samples were compared with those of an unstabilized polypropylene control (Experiment L).

The polypropylene samples can be prepared in the following manner. The stabilizer can be dissolved in acetone or hexane in a concentration of 1 to 5 percent. The stabilizer solution can then be added to the polypropylene (Pro-Fax 6501 by dispersing the stabilizer solutions in the powdered polypropylene using a Henschel blender and agitating at 2,800 rpm. After minutes the typical batch temperature will normally approach 180 F. and a reasonable dispersion of the stabilizers will be obtained. After 10 minutes only traces of the solvent will nonnally remain.

The stabilized polypropylene was injection molded to produce tensile bars, said tensile bars conforming to 'ASTM-D 638-64 T. The tensile bars were aged at 140 C. in a forced airoven. The stress-strain proper-. ties of the original and aged samples were measured by an lnstron. A 4-% inch jaw was used, the jaw separation rate being 1 inch per minute.

Melt index determinations were made on the aged and unaged tensile bars which had been cut upinto small pieces. The melt index test was run according to ASTM-D-l238-62 T, Condition L. As the polymer degrades the molecular weight is reduced by chaim scission. The melt index indicates the molecular weight reduction and is expressed as grams of polymer ex-l truded per unit time. As the molecular weight decreases due todegradation the melt index increases. The test results appear in Table 11.

-0nedayatl40C. l Expressed as grams of polymer extruded per 10 minutes.

The above results reveal the stabilization afforded polypropylene by the compounds of the present invention. Whereas the yield tensile of the unstabilized polypropylene (Experiment L) dropped appreciably on aging, the yield tensile of the polypropylenestabilized with the compounds of the present invention (Experiments N-T) dropped only slightly. Whereas the melt index of the unstabilized polypropylene rose on aging to such a value that it was considered to have failed, the melt index of the polypropylene stabilized with the compounds of the present invention rose only slightly on aging.

In addition, a comparison of the polypropylene stabilized with the compounds of the present invention with polypropylene stabilized with a commercial phenolic antioxidant (Experiment M) reveals that on aging the melt index of the latter material rose much more than the melt indices of the former materials.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What 1 claim is:

l. A composition of matter conformingto the following structural formula: 2

wherein R, R and R are alkyl radicals containing from one to 12 carbon atoms, R and R are selected from the group consisting of hydrogen, alkyl radicals containing from one to 12 carbon atoms, cycloalkyl radicals containing from five to nine carbon atoms and aralkyl radicals containing from seven to nine carbon atoms, and R and R are bivalent radicals selected from the group consisting of thio, dithio, methylene, isobutylidene, butylidene, 1,4-(2-butenylene), xy-

lylenes,

R and R are tertiary alkyl radicals containing four to eight carbon atoms and located ortho to the phenolic hydroxyl group and R and R are selected from the group consisting of S-, -CH

and n is a positive integer from O to l 4. The composition of matter according to claim 1 wherein R and R are bivalent radicals selected from the group consisting of methylene, isobutylidene, butylidene, l ,4-( 2-butenylene), xylylenes,

lr/U

and 4,4'-oxydibenzyl. 

2. The composition of matter according to claim 1 wherein R3 and6 are tertiary alkyl radicals containing four to 12 carbon atoms.
 3. The composition of matter according to claim 1 wherein R, R1 and R2 are selected from the group consisting of methyl, ethyl, propyl and isopropyl radicals, R3 and R6 are tertiary alkyl radicals containing four to eight carbon atoms and located ortho to the phenolic hydroxyl group and R4 and R5 are selected from the group consisting of -S-, -CH2-,
 4. The composition of matter according to claim 1 wherein R4 and R5 are bivalent radicals selected from the group consisting of methylene, isobutylidene, butylidene, 1,4-(2-butenylene), xylylenes, 